The TV's are hooked to B/W cameras that feed an image through an RCA jack....into the TV. What I want is to hook a small light that will light up to indicate sound is coming from that particular camera.

Sort of like when a light goes off on the telephone of someone that is hearing impaired to let them know there is an incoming call.

I think it should be just a matter of a small adapter that plugs into the the male end of the wire just prior to it going into the RCA jack ! Does this make more sense ???

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"What would you do if your legs got decapitated ?"--PoukieBear

I look at her with my head tilted to the side and in a soft voice I just say; You're so pretty !

I think your best bet would be to get or make a small device that lights up when audio is present,
and put "THAT" in the cage with the animals and visible to the cameras.
I'm sure there's a small project like this on hobby websites. It could prolly even be battery operated.

The 'animals' in question.....are Falcons. They are already in the breeding chambers and absolutely cannot be disturbed. Putting anything into the breeding chambers other than food...simply is not an option; but thank you for the suggestion !

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"What would you do if your legs got decapitated ?"--PoukieBear

I look at her with my head tilted to the side and in a soft voice I just say; You're so pretty !

It should not be to hard to do. I'm not sure what the line voltage is on your audio in, but you could use a op amp and relay to turn on the LED if the voltage was above 1/4 max, or even just little bit above the background noise level.

Get a multimeter and measure the voltage on the jack and see what your average voltage is, should be zero with no sound, make some noise and see what voltage you get with sound, and then you could use a comparator to turn on the relay when ever the voltage on the line is above the set voltage. If you know much about electronics it would not be to difficult to build.

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America will only be the Land of the Free as long as it is the Home of the Brave.